The central parsec of the galaxy, identified with the Sagittarius A
nebula, contains ionized gas powered by about 1040 ionizing
photons sec-1
(Lacy el al. 1980).
A cluster of He I emission line stars
has been observed and spectroscopically analyzed
(Tamblyn et al. 1996,
Najarro et al. 1997).
The complete spectrum of
infrared fine structure lines that has been observed, combined with
the H Br and
Br lines (see
Shields & Ferland
1994
for a compilation) should in principle allow to perform an abundance
analysis. From a two-component photoionization model
Shields & Ferland
(1994)
estimate that the abundance of Ar
should be about twice solar, but Ne seems rather to have the solar
value. The evidence for over solar metallicity is thus mixed. The N/O
ratio is estimated to about 3 - 4 times solar. However, the
derived abundances may be clouded by errors in the
reddening corrections (the extinction is as high as
AV = 31, so, even at
far infrared wavelengths, reddening become important) and
uncertainties in the atomic parameters (mainly those determining the
ionization structure). As a consistency check,
Shields & Ferland
(1994)
compared the electron temperature
measured from recombination lines with their model predictions. For
that, they included heating by dust, and assumed the same grain
content as in the model of
Baldwin et al. (1991)
for Orion. They found
the measured temperatures to be consistent with a metallicity 1 - 2
times solar, while 3 times solar would
be only marginally consistent. However, with a population of small
grains, photoelectric heating would be more important, and larger metal
abundances could be acceptable.

The Galactic center has since then been reobserved by ISO
(Lutz et al. 1996),
but a detailed discussion of the new results remains to be
done.